Chrysotile asbestos exposure in the manufacturing of thermal insulating boards

Our plain-English summary of Chrysotile asbestos exposure in the manufacturing of thermal insulating boards, by L.J. Bhagia, J.B. Vyas, M.I. Shaikh, et al (Environmental Monitoring and Assessment, 2010).

The study

• Authors: L.J. Bhagia, J.B. Vyas, M.I. Shaikh, S.L. Dodia
• Journal: Environmental Monitoring and Assessment
• Published: 2010;167(1-4):559-64
• Cited by: 6 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Exposure to asbestos fibers has been extensively studied in milling, mining of asbestos fibers, and in industries manufacturing asbestos-cement sheets, pipes, etc. However, very few studies have been reported in asbestos textiles, brake lining workers, and insulation products. In the present investigation, chrysotile exposure monitoring was carried out in a small thermal insulating boards manufacturing facility. Twenty-eight samples were analyzed from various locations like feeding of raw materials, weighing, pressing, machine grinding, and hand finishing of final products. Twenty-five percent of the samples were found to be above ACGIH TLV of 0.1 fibers per milliliter. However, mean fiber concentrations were found to be lower than 0.1 fibers per milliliter, except for the process of feeding of raw materials where the mean fiber concentration was 0.1087+/-0.0631 fibers per milliliter.

In plain English

This was an air-monitoring survey of chrysotile asbestos in a small factory that made high-temperature thermal insulating boards from a mix of 22% chrysotile fibers and 78% cement. The factory had 11 workers. The authors, from India's National Institute of Occupational Health, collected one-hour air samples from workers' breathing zones at five jobs: feeding raw materials, weighing and slurry making, pressing, machine grinding, and hand finishing. They counted fibers by phase contrast microscopy. Two samples were spoiled, which left 28. Seven of the 28 samples (25%) were above the ACGIH limit of 0.1 fibers per milliliter. Average levels were below that limit except at raw-material feeding, where the mean was 0.1087 fibers per milliliter across 4 samples. The highest single sample, 0.1681, was also taken there. Hand finishing had the lowest mean, 0.0451. Factory medical records showed no cases of asbestosis, and the workers' masks were not NIOSH-approved. The authors concluded that low average levels do not mean disease will not occur, because mesothelioma or lung cancer may appear years after exposure.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Workplace air-monitoring (exposure measurement) survey at a single facility, using personal breathing-zone samplers and phase contrast microscopy (NIOSH method 7400)
• Who was studied: One small thermal insulating board manufacturing facility with 11 workers. Air samples were taken at five work locations. The article does not name the facility's location or the dates of sampling. The authors are based at the National Institute of Occupational Health in Ahmedabad, India.
• Exposure: Chrysotile asbestos fibers in the manufacture of thermal insulating boards (also called syndania sheets) made of 22% chrysotile and 78% cement. Sampling covered feeding of raw materials, weighing and slurry making, pressing, machine grinding, and hand finishing. Six consecutive 1-hour samples were planned per location.
• Main results:
  • Of 28 samples, 7 (25%) were above the ACGIH threshold limit value of 0.1 fibers per milliliter.
  • Feeding of raw materials had the highest mean, 0.1087 plus or minus 0.0631 fibers per milliliter, based on 4 samples. Two of the six feeding samples were spoiled during slide making.
  • The highest single concentration, 0.1681 fibers per milliliter, was measured in feeding of raw materials.
  • Weighing and slurry making had a mean of 0.0571 plus or minus 0.0255 fibers per milliliter (6 samples).
  • Pressing had a mean of 0.0656 plus or minus 0.0378 fibers per milliliter (6 samples).
  • Machine grinding had a mean of 0.0817 plus or minus 0.0437 fibers per milliliter (6 samples). The authors note this process had a local exhaust system with bag filters.
  • Hand finishing had the lowest mean, 0.0451 plus or minus 0.0257 fibers per milliliter (6 samples).
  • The article reported a limit of detection of 0.03 and a limit of quantitation of 0.45 fibers per milliliter for its method.
  • Factory medical records reported no case of asbestosis among the workers. Workers had masks, but the masks were not NIOSH-approved.
• The authors' conclusion: The authors concluded that average fiber levels were below 0.1 fibers per milliliter in all processes except feeding (mean 0.1087). They added that this does not mean disease will not occur in the future, since mesothelioma or lung cancer may occur years after exposure ends. They recommended NIOSH-approved respirators, proper maintenance of dust control, improved housekeeping, and supervisor training.

Topics

Medical terms in this study, explained in our Lexicon: Chrysotile, Asbestos Exposure, Asbestos-Cement, Asbestos Textiles, Brake Lining.

Related studies

• In situ ESEM study of the thermal decomposition of chrysotile asbestos in view of safe recycling of the transformation product — A.F. Gualtieri, M.L. Gualtieri, et al. (2008)
• Thermal modification of chrysotile asbestos: evidence for decreased cytotoxicity — R. Valentine, M.J. Chang, et al. (1983)
• Trends in Airborne Chrysotile Asbestos Fibre Concentrations in Asbestos Cement Manufacturing Factories in Zimbabwe from 1996 to 2016 — B. Mutetwa, D. Moyo, et al. (2021)
• Prediction of Asbestos-Related Diseases (ARDs) and Chrysotile Asbestos Exposure Concentrations in Asbestos-Cement (AC) Manufacturing Factories in Zimbabwe — B. Mutetwa, D. Moyo, et al. (2022)
• Job Exposure Matrix for Chrysotile Asbestos Fibre in the Asbestos Cement Manufacturing (ACM) Industry in Zimbabwe — B. Mutetwa, D. Moyo, et al. (2022)
• Exposure to Amosite-Containing Ceiling Boards in a Public School in Switzerland: A Case Study — D. Vernez, O. Duperrex, et al. (2019)

Browse more research in Environmental Monitoring and Assessment, or return to medical research.